This invention relates to a filter device for filtering a liquid by a filter element received therein.
A conventional filter device, having an exchangeable filter element, is disclosed in Japanese Patent Unexamined Publication No. 7-100310 earlier filed by the Applicant of the present application, and this filter device is shown in FIG. 10.
A cartridge-type filter element 02 is received within a cylindrical casing 01 with a closed bottom, and a set plate 03, serving as a lid, is mounted at an open end (opening) of the casing 01 through an O-ring (seal member) 04 to close the same. A ring nut (ring-shaped fastening member) 05 is threaded on an external-thread portion, formed on an outer peripheral surface of the set plate 03, thereby fixing the set plate 03 to the casing 01.
The O-ring 04, held between the casing 01 and the set plate 03, is compressed axially to form an axial seal, but does not form a radial seal.
Therefore, if the ring nut 05 fails to be completely threaded on the set plate, there is a possibility that the O-ring 04 is not compressed, or is inadequately compressed between the casing 01 and the set plate 03 when tightening the ring nut 05, so that the positive seal is not obtained.
Particularly when a foreign matter is caught in the threaded portions of the ring nut 05 and the set plate 03, or when dust and dirt are present in the thread grooves, there is a possibility that the threaded engagement is not effected completely, and in such a case the seal is incomplete.
This invention has been made in view of the above problems, and an object of the invention is to provide a filter device in which even if a casing and a lid are fastened together somewhat inadequately, a positive seal therebetween is achieved.
The above object has been achieved by a filter device according to a first aspect of the present invention comprising a tubular casing with a closed bottom, a filter element received within the casing, a lid which closes an open end of the casing, and has a communication hole communicating the inside and outside of the casing with each other, and a fastening member fastening the casing and the lid together; wherein a gap is formed between a peripheral wall of the open end portion of the casing and a peripheral surface of that portion of the lid opposed to the peripheral wall; a radial seal width of an annular elastic seal member to be mounted in the gap is larger than a width of the gap in the radial direction; and the seal member closes the gap liquid-tight in the radial direction when the filter device is assembled.
The radial seal width of the annular elastic seal member to be mounted in the gap, formed between the peripheral wall of the open end portion of the casing and the peripheral surface of that portion of the lid opposed to the peripheral wall, is larger than the width of the gap in the radial direction, and therefore during the assembling operation, the elastic seal member, while compressed in the radial direction, is press-fitted into the gap, and therefore even if the fastening of the lid to the casing by the fastening member is somewhat inadequate, the liquid-tight seal is formed, thereby maintaining the sealing effect.
The above object has also been achieved by a filter device according to a second aspect of the present invention comprising a tubular casing with a closed bottom which includes a barrel portion having an open distal end portion formed into a different-diameter portion, different in diameter from the barrel portion, through a step portion, a filter element received within the casing, a lid which closes the open end of the barrel, and has a communication hole communicating the inside and outside of the casing with each other, and a fastening member fastening the casing and the lid together; wherein the lid includes a peripheral portion opposed to the step portion of the casing in an axial direction, and an opposed peripheral wall opposed to the different-diameter portion in a radial direction, so that the peripheral portion and the opposed peripheral wall cooperate with the step portion and the different-diameter portion of the casing to form a gap; and an annular elastic seal member, mounted in the gap, is held between the step portion of the casing and the peripheral portion of the lid, and is compressed in the axial direction during an assembling operation, so that the seal member is expanded and deformed in the radial direction, thereby forming a liquid-tight seal between the different-diameter portion of the casing and the opposed peripheral wall of the lid.
When the lid is fastened to the casing by the fastening member, the elastic seal member is compressed in the axial direction between the step portion of the casing and the peripheral portion of the lid, so that the elastic seal member is expanded and compressed in the radial direction, thereby forming the liquid-tight seal between the different-diameter portion of the casing and the opposed peripheral wall of the lid. Therefore, if the seal member is compressed to a certain degree in the axial direction by the fastening operation, the positive seal can be achieved even if the fastening is somewhat inadequate.
In the above-mentioned filter device according to the first and second aspect of the invention of claim 3, it is advantageous that the open edge of the peripheral wall of the open end portion of the casing is bent in a direction to avoid the seal member fitted on the peripheral surface of the lid.
During the assembling operation, the elastic seal member is forced into the radial gap, and therefore the open end edge of the peripheral wall of the casing, forming the gap, is bent so as to avoid the seal member during the assembling operation, and with this construction, the seal member can be inserted into the gap without damaging the seal member, and the good sealing effect can be maintained.
In the above-mentioned filter device, it is preferable that an indication portion is provided on an outer surface of the casing and is covered with a heat-shrinkable member having a light-transmitting property.
The indication portion is covered with the heat-shrinkable member having the light-transmitting property, and therefore an indication on the indication portion can be seen through the heat-shrinkable member. When the contents of the indication can not be clearly seen because of damage or the like, the heat-shrinkable member is peeled or removed, and a new indication portion is provided, and then is covered with a new heat-shrinkable member. By doing so, the indication portion can be easily exchanged, and the indication on the indication portion can always be kept in a clearly-seen condition with such a simple operation at a low cost.
The heat-shrinkable member protects the indication portion from damage from the exterior.
In the above-mentioned filter device according to the present invention, it is also preferable that the casing is covered with a heat-shrinkable member having an indication portion.
The indication portion is provided at the heat-shrinkable member for covering the casing, and therefore when the indication can not be clearly seen, the heat-shrinkable member is peeled or removed, and a new heat-shrinkable member, having the indication portion, is applied to cover the casing, and therefore this exchange operation can be effected easily.
Further, in the above-mentioned filter device according to the present invention, it is also preferable that the open end of the casing is closed by the lid, and the lid is fastened to the casing by the ring nut, and an indication portion on an outer surface of the barrel portion of the casing is covered with a heat-shrinkable member having a light-transmitting property; and the heat-shrinkable member is provided to cover the barrel portion of the casing over a circumference thereof in such a manner that the heat-shrinkable member is disposed close to the smaller-diameter portion of the ring nut, threaded on the lid, to close a gap between the barrel portion of the casing and the smaller-diameter portion of the ring nut.
The heat-shrinkable member is provided to cover the barrel portion of the casing in such a manner that it closes the gap between the casing and the smaller-diameter portion of the ring nut, and therefore the intrusion of foreign matters, dust and dirt can be prevented.
When the indication portion can not be clearly seen, the heat-shrinkable member is peeled or removed, and a new heat-shrinkable member is applied to cover the casing, and with this simple exchange operation, the indication on the indication portion can always be kept in a clearly-seen condition at a low cost.
The heat-shrinkable member protects the indication portion against damage from the exterior and damage liable to occur when attaching and detaching the ring nut for maintenance purposes.
Furthermore, in the above-mentioned filter device according to the present invention, it is also preferable that the open end of the casing is closed by the lid, and the lid is fastened to the casing by the ring nut, and an indication portion on an outer surface of the barrel portion of the casing is covered with a heat-shrinkable member having a light-transmitting property, and that the heat-shrinkable member is provided to cover the barrel portion of the casing and the outer peripheral surface of the ring nut over a circumference thereof.
The heat-shrinkable member is provided to cover the barrel portion of the casing and the outer peripheral surface of the ring nut over the circumference thereof, and therefore the heat-shrinkable member closes the gap between the casing and the ring nut, thereby completely preventing the intrusion of foreign matter, dust, dirt and water.
When the indication portion can not be clearly seen, the heat-shrinkable member is peeled or removed, and a new heat-shrinkable member is applied to cover the casing and the ring nut, and with this simple exchange operation, the indication on the indication portion can always be kept in a clearly-seen condition at a low cost.
The heat-shrinkable member protects the indication portion against damage from the exterior and damage liable to occur when attaching and detaching the ring nut for maintenance purposes.
In the above-mentioned filter device according to the present invention, it is advantageous that a line of cut is formed axially in the heat-shrinkable member.
The heat-shrinkable member can be torn axially along the cut line without the use of any tool, and therefore can be easily removed from the casing. Therefore, the heat-shrinkable member can be exchanged more easily.